Auditory hypersensitivity
Auditory hypersensitivity is a general term for heighted responses to some kinds of sounds, including responses of discomfort or distress. While most people can find certain sounds annoying or uncomfortable, clinical levels of auditory hypersensitivity can involve unusually negative reactions to sounds that others would consider ordinary or tolerable. Auditory hypersensitivity can restrict people's ability to participate in everyday activities, and it is associated with poorer quality of life and mental health problems.
Nomenclature
The terms auditory hypersensitivity or hypersensitivity to sounds are often used. However, the term "sensitivity" can also be used to describe low-level sensory perceptual functioning, especially the ability to detect or discriminate between sensory stimuli, such as might be affected in hearing loss. This is distinct from the heighened responses such as distress and discomfort that underpin the sort of auditory hypersensitivity discussed in this article, and auditory hypersensitivity is often observed in people whose ability to detect or discriminate between sounds is roughly normal.Other terms used to describe auditory hypersensitivity include decreased sound tolerance,
sound tolerance conditions,
sound intolerance,
auditory hyperresponsiveness or hyperresponsivity,
and auditory over-responsiveness or over-responsivity.
The term hyperacusis is sometimes used as a synonym for auditory hypersensitivity generally; however, it can be used more precisely to refer to a specific type of auditory hypersensitivity, as described below.
Varieties
Some factor analyses and conceptual structures suggest that heightened responsiveness to sounds might be a single dimension along which people vary from experiencing lesser to greater responsiveness. However, these results come from studies of sensory processing patterns in general, and could reflect the large amount of variance explained by the inclusion of items from other modalities or patterns. Many other sources suggest distinct auditory hypersensitivity/sound tolerance conditions can be distinguished from one another. These include conditions like hyperacusis and misophonia, which can often co-occur or be associated with one another, although their symptoms are distinct and separate mechanisms may be involved.Reviews and summaries of auditory hypersensitivity and decreased sound tolerance also sometimes include exploding head syndrome, which refers to the perception of intense noises at the onset of sleep. However, auditory hypersensitivity and decreased sound tolerance refer to reactions to auditory stimuli, which thereby also excludes tinnitus, the perception of sounds such as ringing without an external source. Indeed, tinnitus is generally discussed as a condition that can frequently co-occur with auditory hypersensitivity, rather than as an auditory hypersensitivity or sound tolerance condition in its own right. Similarly, although the postulated condition of tonic tensor tympani syndrome has been suggested as a mechanism that may be involved in the auditory hypersensitivity conditions of hyperacusis and acoustic shock, common symptoms associated with this putative syndrome include sensations of fullness in the ear, chronic pain in or around the ear, muffling or distortion of hearing, and rhythmic or fluttering aural sensations, rather than sensitivity to external sounds as such.
Hyperacusis
Hyperacusis is a condition characterised by a reduced tolerance to sounds at levels/volumes that most people would consider normal and non-troubling. Sounds of a loudness level that would not trouble most people can, for people with hyperacusis, cause be experienced as uncomfortable, unpleasant, intense, frightening, painful, and/or overwhelming. For example, some people with hyperacusis can only tolerate sounds of volumes up to 60-70 dB, or the approximate volume of human conversation.Hyperacusis is sometimes subdivided into the varities of loudness hyperacusis and pain hyperacusis. Pain hyperacusis is characterised by a person experiencing physical pain in the ear in response to sounds that would not be loud enough to cause pain to most people. Loudness hyperacusis is characterised by an unusually threshold for experiencing loudness discomfort, such as by finding sounds of moderate volume to be very loud.
There is some overlap between the symptoms of loudness hyperacusis and of sensory overload, insofar as sensory overload can include negative reactions to the intensity of a sensory stimulus.
Loudness recruitment
Loudness recruitment is characterised by experiencing unusually swift increases in the perceived loudness of sounds relative to the sound's actual volume. As a result, people with loudness recruitment begin to find sounds uncomfortably loud at lower volumes than people in the general population. Loudness recruitment is believed to arise as a consequence of poorer hearing acuity, potentially due to damage to the outer hair cells of the cochlea.Importantly, although the two have sometimes been confused, loudness recruitment is not the same phenomenon as loudness hyperacusis. At particularly high sound intensities/volumes, perceived loudness for listeners with normal hearing eventually catches up to and matches perceived loudness for people with loudness recruitment, whereas people with loudness hyperacusis continue to experience unusually strong discomfort to sounds even when most people would find them quite loud.
Misophonia
Misophonia is characterised by an abnormally strong emotional or physiological reaction to specific, everyday sounds which are not loud or even noticed by others, as well as other sensory stimuli associated with those sounds. Reactions to trigger sounds can include frustration, anxiety, anger, a need to leave or stop the sound, disgust, as well as physiological arousal. Triggers are often repetitive oral or nasal sounds like chewing, swallowing, slurping, throat clearing, or sniffling, but other sounds like repetitive pen clicks, clock ticking, footsteps, and typing are also common misophonia triggers.In contrast to hyperacusis and loudness recruitment, misophonic responses are not caused by a sound's loudness, but by the pattern of the sound or even what the sound means to a person. Misophonia is also considered to be distinct from the annoyance caused by ambient environmental sounds, such as background chatter. Negative reactions to being surrounded by many sensory stimuli at once might fall within the concept of sensory overload and overwhelm, rather than misophonia.
Phonophobia
Phonophobia is a specific phobia of particular sounds or classes of sounds. While most people could fear certain loud or threatening sounds, phonophobia refers explicitly to disproportionate and irrational fears of sounds.Unlike other decreased sound tolerance or auditory hypersensitivity conditions described here, phonophobia does not directly involve discomfort caused by sounds. It can arise as a consequence of other forms of auditory hypersensitivity, but for someone with another auditory hypersensitivity condition like hyperacusis or misophonia to also have phonophobia, their level of phonophobic fear, anxiety, and avoidance would need to exceed what could be expected from the discomfort or pain caused by their other auditory hypersensitivity conditions.
Noise sensitivity
Noise sensitivity refers to individual differences in how much annoyance people experience due to ambient and background noise, such as traffic. There is little relationship between noise sensitivity and noise exposure.In contrast to auditory hypersensitivity conditions like hyperacusis and misophonia, noise sensitivity is conceptualised as a personality trait. How noise sensitivity relates to auditory hypersensitivity conditions is poorly researched. Individuals with hyperacusis report high levels of noise sensitivity. However, in contrast to hyperacusis, noise sensitivity in the general population does not necessarily substantially change the steepness of the relationship between sounds' actual volume and perceived loudness.
Auditory distractibility
Distraction caused by background noise can have considerable effects on cognitive performance, although the precise ways in which irrelevant sounds affect performance may differ somewhat across tasks and populations. So far, limited research has attempted to bridge gaps between studying auditory distractibility in controlled laboratory environments and everyday, real-world environments, but performance on experimental measures of auditory attentional capture can be related to one's self-reported propensity towards experiencing distractibility and inattention in general.Some studies suggest that sound intolerance and distraction caused by sounds could be related but distinct phenomena. For example, in the general population, how much sounds in workplaces are distracting and affect workplace job performance seems to constitute a somewhat different dimension from the annoyance caused by the sounds. How much hearing irrelevant speech interferes with one's task performance is only weakly related to self-reported noise sensitivity. Similarly, an autism study suggests that how much one's attention tends to be captured by distracting auditory stimuli in one's environment appears to be somewhat distinguishable from one's propensity towards experiencing noise distress.
Acoustic shock
Acoustic shock refers to putative injuries that are believed to be caused by brief, unexpected, loud sounds, such as feedback in headsets in telephone call centres. There has been controversy over the validity of the condition and whether it is indeed auditory or psychogenic.Acoustic shock is sometimes described as a type of auditory hypersensitivity, but other sources do not list it as a sound tolerance condition or form of auditory hypersensitivity. Its symptoms can include hyperacusis and noise sensitivity, but the most common symptoms may be chronic pain and tinnitus even when no sound is present. Auditory hypersensitivity and sound tolerance conditions are often understood to refer directly to reactions to auditory stimulation.